The goals of this project are: 1. To isolate and clone the DNA for the cocaine receptor (or dopamine transporter); 2. To isolate and clone the DNA for the Dl dopamine receptor and its variants; 3. To search for variants of the D2 dopamine; and 4. To determine the gene expression responsivity of the above receptors. The receptor for cocaine is the dopamine transporter protein on which cocaine acts to release dopamine. The released dopamine activates the high-affinity states of Dl and D2 dopamine receptors to elicit psychomotor behavior associated with euphoria, self-reward and addiction. Since Dl full agonist drugs are recognized by animals as being cocaine, and since Dl antagonists successfully block the action of cocaine, the Dl receptor is important in mediating the behavioral effects of cocaine. Moreover, since Dl and D2 are biochemically linked, D2 receptors play an additional role in mediating cocaine's actions. The cocaine receptor will be isolated by means of our newly developed [125I]FAPP photoaffinity label which is selective for the dopamine transporter. Serial chromatographic procedures ensure that a single protein will be isolated. Partial peptide sequences from this pure material will permit the preparation of oligonucleotide probes to detect and isolate the complete transporter or receptor for cocaine. The Dl dopamine receptor DNA will be obtained via homology probing by means of the polymerase chain reaction. Preliminary data reveal a clone which may have Dl properties D2 receptor variants will also be sought by such homology probing methods. Finally, we intend to examine the speed of change of synthesis of messenger RNA for the cocaine receptor as well as for the Dl and D2 receptors upon antipsychotic or cocaine administration to rats. The availability of clones for these receptors would facilitate new drug design and provide new markers for disease linkage studies in families.